Make export worker page size into a knob (#38327)

Make it a knob so we can adjust it for different use cases.

GitOrigin-RevId: e62594c20f0e9cd5182194d78c3105af0eb9bf03

Author: nipunn1313

crates/application/src/exports/mod.rs

@@ -10,6 +10,7 @@ use common::{
         ComponentPath,
     },
     fastrace_helpers::get_sampled_span,
+    knobs::EXPORT_WORKER_PAGE_SIZE,
     persistence::LatestDocument,
     runtime::Runtime,
     types::{
@@ -146,7 +147,10 @@ where
                     );
                 }
             }
-            let table_iterator = worker.database.table_iterator(ts, 1000).multi(tablet_ids);
+            let table_iterator = worker
+                .database
+                .table_iterator(ts, *EXPORT_WORKER_PAGE_SIZE)
+                .multi(tablet_ids);
 
             let zipper = construct_zip_snapshot(
                 worker,

crates/common/src/knobs.rs

@@ -1298,6 +1298,10 @@ pub static EXPORT_MAX_INFLIGHT_PREFETCH_BYTES: LazyLock<usize> = LazyLock::new(|
     .clamp(1, u32::MAX as usize)
 });
 
+/// The page size to the table iterator in the export worker.
+pub static EXPORT_WORKER_PAGE_SIZE: LazyLock<usize> =
+    LazyLock::new(|| env_config("EXPORT_WORKER_PAGE_SIZE", 1000));
+
 /// Whether or not a service should propagate all upstream traces or perform its
 /// own sampling
 pub static PROPAGATE_UPSTREAM_TRACES: LazyLock<bool> =